$("#scratch").height($("#scratch").width() * 0.625+ "px")

// theCanvas = document.getElementById('scratch');
// var context = theCanvas.getContext('2d');
// context.fillStyle = 'rgba(255, 255, 255, 0)';

VerletJS.prototype.spider = function (origin) {
    var i;
    var legSeg1Stiffness = 0.99;
    var legSeg2Stiffness = 0.99;
    var legSeg3Stiffness = 0.99;
    var legSeg4Stiffness = 0.99;

    var joint1Stiffness = 1;
    var joint2Stiffness = 0.4;
    var joint3Stiffness = 0.9;

    var bodyStiffness = 1;
    var bodyJointStiffness = 1;

    var composite = new this.Composite();
    composite.legs = [];


    composite.thorax = new Particle(origin);
    composite.head = new Particle(origin.add(new Vec2(0, -5)));
    composite.abdomen = new Particle(origin.add(new Vec2(0, 10)));

    composite.particles.push(composite.thorax);
    composite.particles.push(composite.head);
    composite.particles.push(composite.abdomen);

    composite.constraints.push(new DistanceConstraint(composite.head, composite.thorax, bodyStiffness));


    composite.constraints.push(new DistanceConstraint(composite.abdomen, composite.thorax, bodyStiffness));
    composite.constraints.push(new AngleConstraint(composite.abdomen, composite.thorax, composite.head, 0.4));


    // legs
    for (i = 0; i < 4; ++i) {
        composite.particles.push(new Particle(composite.particles[0].pos.add(new Vec2(3, (i - 1.5) * 3))));
        composite.particles.push(new Particle(composite.particles[0].pos.add(new Vec2(-3, (i - 1.5) * 3))));

        var len = composite.particles.length;

        composite.constraints.push(new DistanceConstraint(composite.particles[len - 2], composite.thorax, legSeg1Stiffness));
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 1], composite.thorax, legSeg1Stiffness));


        var lenCoef = 1;
        if (i == 1 || i == 2)
            lenCoef = 0.7;
        else if (i == 3)
            lenCoef = 0.9;

        composite.particles.push(new Particle(composite.particles[len - 2].pos.add((new Vec2(20, (i - 1.5) * 30)).normal().mutableScale(20 * lenCoef))));
        composite.particles.push(new Particle(composite.particles[len - 1].pos.add((new Vec2(-20, (i - 1.5) * 30)).normal().mutableScale(20 * lenCoef))));

        len = composite.particles.length;
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 4], composite.particles[len - 2], legSeg2Stiffness));
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 3], composite.particles[len - 1], legSeg2Stiffness));

        composite.particles.push(new Particle(composite.particles[len - 2].pos.add((new Vec2(20, (i - 1.5) * 50)).normal().mutableScale(20 * lenCoef))));
        composite.particles.push(new Particle(composite.particles[len - 1].pos.add((new Vec2(-20, (i - 1.5) * 50)).normal().mutableScale(20 * lenCoef))));

        len = composite.particles.length;
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 4], composite.particles[len - 2], legSeg3Stiffness));
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 3], composite.particles[len - 1], legSeg3Stiffness));


        var rightFoot = new Particle(composite.particles[len - 2].pos.add((new Vec2(20, (i - 1.5) * 100)).normal().mutableScale(12 * lenCoef)));
        var leftFoot = new Particle(composite.particles[len - 1].pos.add((new Vec2(-20, (i - 1.5) * 100)).normal().mutableScale(12 * lenCoef)))
        composite.particles.push(rightFoot);
        composite.particles.push(leftFoot);

        composite.legs.push(rightFoot);
        composite.legs.push(leftFoot);

        len = composite.particles.length;
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 4], composite.particles[len - 2], legSeg4Stiffness));
        composite.constraints.push(new DistanceConstraint(composite.particles[len - 3], composite.particles[len - 1], legSeg4Stiffness));


        composite.constraints.push(new AngleConstraint(composite.particles[len - 6], composite.particles[len - 4], composite.particles[len - 2], joint3Stiffness));
        composite.constraints.push(new AngleConstraint(composite.particles[len - 6 + 1], composite.particles[len - 4 + 1], composite.particles[len - 2 + 1], joint3Stiffness));

        composite.constraints.push(new AngleConstraint(composite.particles[len - 8], composite.particles[len - 6], composite.particles[len - 4], joint2Stiffness));
        composite.constraints.push(new AngleConstraint(composite.particles[len - 8 + 1], composite.particles[len - 6 + 1], composite.particles[len - 4 + 1], joint2Stiffness));

        composite.constraints.push(new AngleConstraint(composite.particles[0], composite.particles[len - 8], composite.particles[len - 6], joint1Stiffness));
        composite.constraints.push(new AngleConstraint(composite.particles[0], composite.particles[len - 8 + 1], composite.particles[len - 6 + 1], joint1Stiffness));

        composite.constraints.push(new AngleConstraint(composite.particles[1], composite.particles[0], composite.particles[len - 8], bodyJointStiffness));
        composite.constraints.push(new AngleConstraint(composite.particles[1], composite.particles[0], composite.particles[len - 8 + 1], bodyJointStiffness));
    }

    this.composites.push(composite);
    return composite;
}

VerletJS.prototype.spiderweb = function (origin, radius, segments, depth) {
    var stiffness = 0.6;
    var tensor = 0.3;
    var stride = (2 * Math.PI) / segments;
    var n = segments * depth;
    var radiusStride = radius / n;
    var i, c;

    var composite = new this.Composite();

    // particles
    for (i = 0; i < n; ++i) {
        var theta = i * stride + Math.cos(i * 0.4) * 0.05 + Math.cos(i * 0.05) * 0.2;
        var shrinkingRadius = radius - radiusStride * i + Math.cos(i * 0.1) * 20;

        var offy = Math.cos(theta * 2.1) * (radius / depth) * 0.2;
        composite.particles.push(new Particle(new Vec2(origin.x + Math.cos(theta) * shrinkingRadius, origin.y + Math.sin(theta) * shrinkingRadius + offy)));
    }

    for (i = 0; i < segments; i += 4)
        composite.pin(i);

    // constraints
    for (i = 0; i < n - 1; ++i) {
        // neighbor
        composite.constraints.push(new DistanceConstraint(composite.particles[i], composite.particles[i + 1], stiffness));

        // span rings
        var off = i + segments;
        if (off < n - 1)
            composite.constraints.push(new DistanceConstraint(composite.particles[i], composite.particles[off], stiffness));
        else
            composite.constraints.push(new DistanceConstraint(composite.particles[i], composite.particles[n - 1], stiffness));
    }


    composite.constraints.push(new DistanceConstraint(composite.particles[0], composite.particles[segments - 1], stiffness));

    for (c in composite.constraints)
        composite.constraints[c].distance *= tensor;

    this.composites.push(composite);
    return composite;
}

//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com/array/shuffle [v1.0]
function shuffle(o) { //v1.0
    for (var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x);
    return o;
}

VerletJS.prototype.crawl = function (leg) {

    var stepRadius = 100;
    var minStepRadius = 35;

    var spiderweb = this.composites[0];
    var spider = this.composites[1];

    var theta = spider.particles[0].pos.angle2(spider.particles[0].pos.add(new Vec2(1, 0)), spider.particles[1].pos);

    var boundry1 = (new Vec2(Math.cos(theta), Math.sin(theta)));
    var boundry2 = (new Vec2(Math.cos(theta + Math.PI / 2), Math.sin(theta + Math.PI / 2)));


    var flag1 = leg < 4 ? 1 : -1;
    var flag2 = leg % 2 == 0 ? 1 : 0;

    var paths = [];

    var i;
    for (i in spiderweb.particles) {
        if (
            spiderweb.particles[i].pos.sub(spider.particles[0].pos).dot(boundry1) * flag1 >= 0
            && spiderweb.particles[i].pos.sub(spider.particles[0].pos).dot(boundry2) * flag2 >= 0
        ) {
            var d2 = spiderweb.particles[i].pos.dist2(spider.particles[0].pos);

            if (!(d2 >= minStepRadius * minStepRadius && d2 <= stepRadius * stepRadius))
                continue;

            var leftFoot = false;
            var j;
            for (j in spider.constraints) {
                var k;
                for (k = 0; k < 8; ++k) {
                    if (
                        spider.constraints[j] instanceof DistanceConstraint
                        && spider.constraints[j].a == spider.legs[k]
                        && spider.constraints[j].b == spiderweb.particles[i]) {
                        leftFoot = true;
                    }
                }
            }

            if (!leftFoot)
                paths.push(spiderweb.particles[i]);
        }
    }

    for (i in spider.constraints) {
        if (spider.constraints[i] instanceof DistanceConstraint && spider.constraints[i].a == spider.legs[leg]) {
            spider.constraints.splice(i, 1);
            break;
        }
    }

    if (paths.length > 0) {
        shuffle(paths);
        spider.constraints.push(new DistanceConstraint(spider.legs[leg], paths[0], 1, 0));
    }
}

window.onload = function () {
    var canvas = document.getElementById("scratch");

    // canvas dimensions
    var width = parseInt(canvas.style.width);
    var height = parseInt(canvas.style.height);

    // retina
    var dpr = window.devicePixelRatio || 1;
    canvas.width = width * dpr;
    canvas.height = height * dpr;
    canvas.getContext("2d").scale(dpr, dpr);

    // simulation
    var sim = new VerletJS(width, height, canvas);

    // entities
    var spiderweb = sim.spiderweb(new Vec2(width / 2, height / 2), Math.min(width, height) / 2, 20, 7);

    var spider = sim.spider(new Vec2(width / 2, -300));


    spiderweb.drawParticles = function (ctx, composite) {
        var i;
        for (i in composite.particles) {
            var point = composite.particles[i];
            ctx.beginPath();
            ctx.arc(point.pos.x, point.pos.y, 1.3, 0, 2 * Math.PI);
            ctx.fillStyle = "#2dad8f";
            ctx.fill();
        }
    }


    spider.drawConstraints = function (ctx, composite) {
        var i;

        ctx.beginPath();
        ctx.arc(spider.head.pos.x, spider.head.pos.y, 4, 0, 2 * Math.PI);
        ctx.fillStyle = "#000";
        ctx.fill();

        ctx.beginPath();
        ctx.arc(spider.thorax.pos.x, spider.thorax.pos.y, 4, 0, 2 * Math.PI);
        ctx.fill();

        ctx.beginPath();
        ctx.arc(spider.abdomen.pos.x, spider.abdomen.pos.y, 8, 0, 2 * Math.PI);
        ctx.fill();

        for (i = 3; i < composite.constraints.length; ++i) {
            var constraint = composite.constraints[i];
            if (constraint instanceof DistanceConstraint) {
                ctx.beginPath();
                ctx.moveTo(constraint.a.pos.x, constraint.a.pos.y);
                ctx.lineTo(constraint.b.pos.x, constraint.b.pos.y);

                // draw legs
                if (
                    (i >= 2 && i <= 4)
                    || (i >= (2 * 9) + 1 && i <= (2 * 9) + 2)
                    || (i >= (2 * 17) + 1 && i <= (2 * 17) + 2)
                    || (i >= (2 * 25) + 1 && i <= (2 * 25) + 2)
                ) {
                    ctx.save();
                    constraint.draw(ctx);
                    ctx.strokeStyle = "#000";
                    ctx.lineWidth = 3;
                    ctx.stroke();
                    ctx.restore();
                } else if (
                    (i >= 4 && i <= 6)
                    || (i >= (2 * 9) + 3 && i <= (2 * 9) + 4)
                    || (i >= (2 * 17) + 3 && i <= (2 * 17) + 4)
                    || (i >= (2 * 25) + 3 && i <= (2 * 25) + 4)
                ) {
                    ctx.save();
                    constraint.draw(ctx);
                    ctx.strokeStyle = "#000";
                    ctx.lineWidth = 2;
                    ctx.stroke();
                    ctx.restore();
                } else if (
                    (i >= 6 && i <= 8)
                    || (i >= (2 * 9) + 5 && i <= (2 * 9) + 6)
                    || (i >= (2 * 17) + 5 && i <= (2 * 17) + 6)
                    || (i >= (2 * 25) + 5 && i <= (2 * 25) + 6)
                ) {
                    ctx.save();
                    ctx.strokeStyle = "#000";
                    ctx.lineWidth = 1.5;
                    ctx.stroke();
                    ctx.restore();
                } else {
                    ctx.strokeStyle = "#000";
                    ctx.stroke();
                }
            }
        }
    }

    spider.drawParticles = function (ctx, composite) {
    }

    // animation loop
    var legIndex = 0;
    var loop = function () {
        if (Math.floor(Math.random() * 4) == 0) {
            sim.crawl(((legIndex++) * 3) % 8);
        }

        sim.frame(16);
        sim.draw();
        requestAnimFrame(loop);
    };

    loop();
};
